Fired because im not friends with facebook?

[Britt]

I was recently terminated from my at will employment position for not "adhering to their social media policy". their policy states that I must be friends with their page on facebook. I was friends with them, however my status updates were set to private so they could not see them. everything I wrote was still visible to them on my wall. my question is, is it illegal for them to state an invalid reason for my termination? there is employees there who are not friends with their page, and they have not received any type of warning for not being their friend